|Publication number||US4572714 A|
|Application number||US 06/644,149|
|Publication date||Feb 25, 1986|
|Filing date||Aug 24, 1984|
|Priority date||Dec 24, 1980|
|Also published as||DE3170064D1, EP0055142A2, EP0055142A3, EP0055142B1|
|Publication number||06644149, 644149, US 4572714 A, US 4572714A, US-A-4572714, US4572714 A, US4572714A|
|Inventors||Takashi Suzuki, Ryohei Fukuda, Kouji Takahashi|
|Original Assignee||Fuji Jukogyo Kabushiki Kaisha|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (9), Referenced by (32), Classifications (16), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a continuation of application Ser. No. 332,045, filed 12-18-81, abandoned.
The present invention relates to a router bit useful to trim a composite material made by impregnating resin into laminated cloth made of carbon fiber or Kevler (trademark).
Since such a composite material has high weight and high strength, the material is used for making the body of an aircraft or vehicle. The characteristics of the composite material is varied dependent on the type of combined materials, treatment temperature, construction and other factors. Therefore, it is very difficult to cut the composite material.
FIG. 6a shows a section of material b in trimming with a right-hand router bit a, FIG. 6b shows a section with a left-hand router bit a' and FIG. 6c shows a section with a strait fluted bit a". In the trimming with the right-hand router bit a, fluff and burrs are left on the surface of the material, and with the left-hand rooter but a', fluff and burrs are left on the underside of the material, and with the straight fluted bit a", fluff and burrs are formed on both sides. In addition, a distance between the position of the trimming and an edge of a clamping jig c must be provided. Accordingly, the material vibrates about the trimming portion, which causes delamination, a decrease of strength and fatigue fracture of the composite material.
An object of the present invention is to provide a router bit which can cut a composite material without leaving fluff and burrs on the material.
Another object of the present invention is to provide a router bit which is capable of preventing the vibration of the material during the cutting.
According to the present invention, there is provided a router bit comprising a shank and a fluted portion, the fluted portion comprising at least two continuous upper cutting edges higher than a predetermined standard line and at least two continuous cutting edges lower than the standard point, helixes of the upper and lower cutting edges being twisted in the opposite direction each other and overlapping in a limited overlapping range at the standard point, said overlapping range being substantially less than the length of said fluted portion the axial length of the overlapping range being less than 1/10 of the outermost diameter of said fluted portion, said fluted portion being formed with cutter edges on the point of said bit for drilling a material, at least one of said upper cutting edges being different from the other of said upper cutting edges in length and at least one of said lower cutting edges being different from the other of said lower cutting edges in length, and ends of the cutting edges in the overlapping range being equiangularly disposed.
Other objects and features of the present invention will be fully described with reference to the accompanying drawings.
FIG. 1 is a side view of a router bit according to the present invention;
FIG. 2 is an enlarged sectional view of a portion of the router bit taken along the line X--X of FIG. 1;
FIG. 3 is an exploded perspective view illustrating a relationship between a composite material and a clamping jig;
FIG. 4 is a sectional view of a composite material clamping by a clamp shown in elevational view;
FIG. 5 is a sectional view showing a trimming operation with the router bit of FIG. 1;
FIGS. 6a to 6c show trimming operations with conventional router bits;
FIG. 7 is a side view partly broken-away showing another embodiment of the present invention;
FIG. 8 is a perspective view illustrating a relation between a composite material and a clamping jig;
FIG. 9 is a perspective view partly broken-away showing a part of a clamped state of the material; and
FIG. 10 is a sectional view partly broken-away showing a trimming operation with the router bit of FIG. 7.
Referring to FIGS. 1 and 2, reference numeral 1 designates a two-fluted router bit having a shank 1a and a fluted portion 2. The fluted portion 2 comprises an upper fluted portion and a lower fluted portion, with respect to a standard line A. The upper fluted portion comprises two upper cutting edges 4 and the lower fluted portion comprises two lower cutting edges 3. The upper cutting edges 4 are twisted in a counter-clockwise direction and the lower cutting edges 3 are twisted in a clockwise direction. The helix angle α of the lower cutting edge 3 is equal to the helix angle β of the upper cutting edge 4. The flute length of the upper portion is equal to that of the lower portion. As shown in FIG. 2, each of the cutting edges 3 and 4 has an axial rake angle θ1(positive), a primary relief angle θ2 and a secondary clearance angle θ3. The cutting edges 3 and 4 overlap each other over a range d (FIG. 1) at the standard line A. Flutes of both portions also overlap each other. On the point of the bit, cutting cutter edges 5 are provided for drilling the material.
Describing a cutting operation with the router bit with reference to FIGS. 3 to 5, a plane composite material 11 is put on supports 12 and a trimming jig 13 is put on the composite material 11. At suitable positions of the material 11 and jig 13, a plurality of tooling holes 15 are provided, corresponding holes formed in both members being in alignment with each other. A tooling pin 14 is inserted into corresponding holes 15 and both members are clamped by a clamp 16 as shown in FIG. 4.
As shown in FIG. 5, the router bit 1 is fixed to a hand router 17 having a profiling stylus 18. The hand router 17 is so disposed that the standard line A is positioned at a location substantially equal to the center of the thickness of the material 11. The hand router 17 is moved along a contour (template) 13a of the triming jig 13, so that the composite material is trimmed by the router bit 1.
Since the lower cutting edges 3 are twisted in a clockwise direction and the upper cutting edges 4 are twisted in a counterclockwise direction, fluff raised by both cutting edges is oriented toward the central portion of the width of the material and is perfectly cut of by the cutting edges 3 and 4. Therefore fluff and burrs do not remain on both surfaces of the composite material 11.
Since the helix angles α and β of both cutting edges are substantially equal to each other, the force exerted on the material in the upper direction, which occurs by the lower cutting edges 3, and the force in the lower direction caused by the upper cutting edges 4 balance each other. Therefore, the composite material does not vibrate to a great degree in spite of an offset distance δ. Thus, delamination of the composite material may be prevented.
It is necessary to decrease the overlap range d so as to be as small as possible in order to prevent vibration of the material 11. A preferable length of the overlap range d is less than 1/10 of the bit diameter D. A preferable helix angle α(β) is less than 40° in order to obtain a smooth cut face and to prevent the vibration of the material. A preferable axial rake angle θ1 and a primary relief angle θ2 are between 10° and 20° and the most preferable angle is 15°. It is preferable to select the secondary clearance angle θ3 between 30° and 40° and the most preferable angle is 35°.
An example of the router bit according to the present invention is as follows:
Bit diameter: 3/16 in. (4.76 mm), two-fluted bit;
Helix angle of the lower cutting edge: 30°
Helix angle of the upper cutting edge: 30°
Overlap length: 0.45 mm
Shank diameter: 1/4 in. (6.35 mm)
Material: cemented carbide
An experiment was conducted to trim a plane composite material with the above rooter bit at 23,000 rpm. A smooth cut face without fluff, burrs and delamination was obtained. Further it was confirmed that a reliable drilling of the material was carried out with a router bit having a point angle θ of 135°.
Cutting speed with conventional bits as shown in FIGS. 6a to 6c is 500 mm/min at most, since the cutting speed cannot be increased because of a low cutting ability. To the contrary, it is possible to increase the cutting speed to 3500 mm/min with the router bit of the present invention. In addition, durability of the bit may be increased by properly selecting the cutting edge angles θ1, θ2 and θ3. Durability of the router bit according to the present invention is about six times as long as that of a conventional bit.
FIG. 7 shows another embodiment of the present invention. Although the illustrated router bit is a four-fluted bit, the present invention is not limited to such a bit. In the drawings, the same parts as the router bit of FIG. 1 are identified by the same references. The routerf bit has a suitable axial rake angle θ1, a primary relief angle θ2 and a secondary clearance angle θ3. The helix angle α of the lower cutting edge 3 having a right-hand helix is different from the helix angle β of the upper cutting edge 4 having a left-hand helix. For example, the angle α is about 45° and β is about 10°. In the overlap range, one cutting edge 3a of the lower cutting edges 3 is longer than the other cutting edge 3b, and the upper cutting edge 4a is longer than the cutting edge 4b, but the ends of these cutting edges are equiangularly disposed in cross section.
Referring to FIG. 8 showing a composite material having a convex shape which is put on a lower form 22 set on a table 24 and an upper form 23 is put on the material 21. The material is clamped by a clamp using pins 26 inserted into holes 25 in the same manner as the previous embodiment.
Generally a composite material used for an aircraft has a complex curvature in section and often includes a honeycomb core as shown in FIG. 10. The upper form 23 can be exactly formed into the shape of the composite material to be trimmed from a master model. However, it is difficult to form the lower form 22 into the underside shape of the material including the honeycomb core. Accordingly, inevitably a gap G is left between the material 21 and the lower form 22 as shown in FIG. 10. Therefore, when the material is trimmed with a conventional end mill or bit, the material vibrates primarily because of the gap G, which will cause delamination of the material and a great deal of burrs.
In accordance with the router bit of the second embodiment, since the helix angle α of the lower cutting edge 3 is greater than the angle β of the upper cutting edge 4, the composite material 21 is drawn up and pressed against the upper form 23 and held in such a condition. Thus, the composite material can be trimmed with the rooter bit without vibrating and occurrence of delamination.
Since there is provided double cutting edges in the overlap range compared with the upper or lower cutting edges, burrs aggregated about the standard line A may be perfectly cut off to provide a smooth cut face.
It is preferable to select the helix angle β less than 1/3 of the helix angle α. The axial rake angle θ1 (posituve) of the router bit of FIG. 7 is preferably between 15° and 25° and 20° is the most preferable. The preferably primary relief angle θ2 is between 10° and 20° and 15° is the most preferable. The secondary clearance angle θ3 is selected between 20° and 30° and the most preferable angle is 25°.
An example of the router bit of the second embodiment has a bit diameter of 1/4 in. (6.35 mm, four-fluted bit), a cutting edge angle α of 45° and a cutting edge angle β of 10°.
Although the composite material 21 of FIG. 8 has an upper surface as a standard surface, a composite material having an underside as a standard surface is trimmed by another router bit having an upper cutting edge of a large helix angle β and a lower cutting edge of a small helix angle α. Thus, the material is pressed against a lower standard form and trimmed in the same manner as the above-described embodiment.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US2778252 *||Sep 26, 1956||Jan 22, 1957||Nat Twist Drill & Tool Company||Self-thinned heavy-duty twist drill structure|
|US3701188 *||Jan 14, 1971||Oct 31, 1972||Wall Machine Works||Helically fluted router bit|
|US3749189 *||Mar 1, 1971||Jul 31, 1973||Werkzeugbau Gmbh||Rock drilling bit|
|US3913196 *||Aug 29, 1974||Oct 21, 1975||Lear Siegler Inc||Rotary cutting tool|
|US4227837 *||Oct 12, 1978||Oct 14, 1980||Shigeyasu Yodoshi||Router bit|
|US4274771 *||Jun 28, 1979||Jun 23, 1981||G. N. Tool Inc.||Boring reamer with end mill cutters|
|US4395167 *||Mar 9, 1981||Jul 26, 1983||National Carbide Tool, Inc.||Router especially for use as a fiber-metal cutter|
|US4475850 *||Aug 16, 1981||Oct 9, 1984||Penoza Frank J||Split helix router bit|
|US4480949 *||May 28, 1982||Nov 6, 1984||The Boeing Company||Combination opposed helix router for routing composite material face sheets having honeycomb core|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US4795289 *||Mar 27, 1986||Jan 3, 1989||Potemkin Gennady Y||Reamer|
|US5049009 *||Aug 21, 1990||Sep 17, 1991||The Weldon Tool Company||Improved cutting tool|
|US5176476 *||Sep 25, 1989||Jan 5, 1993||The Boeing Company||Router cutting bit|
|US5188488 *||Jul 10, 1992||Feb 23, 1993||Mitsubishi Materials Corporation||End mill|
|US5201619 *||Jan 27, 1992||Apr 13, 1993||Hitachi Tool Kabushiki Kaisha||Tapered slot end mill|
|US5294219 *||Dec 22, 1992||Mar 15, 1994||Mitsubishi Materials Corporation||Ball end mill|
|US6102636 *||Jun 2, 1998||Aug 15, 2000||Geise; Samuel C.||Hydraulically powered spindle for working metals and composite materials|
|US6637987||Feb 26, 2002||Oct 28, 2003||Choon Nang Electrical Appliance Mfy., Ltd.||Drill bit|
|US6758639 *||Feb 7, 2002||Jul 6, 2004||Credo Technology Corporation||Bit for cutting drywall|
|US7090442 *||Dec 9, 2003||Aug 15, 2006||The Boeing Company||Shaper router and method|
|US7101125 *||Dec 17, 2003||Sep 5, 2006||Kennametal Inc.||Twist drill|
|US7223053 *||Sep 1, 2004||May 29, 2007||Berkshire Precision Tool, Llc||Helical flute end mill with multi-section cutting edge|
|US7600953 *||Oct 13, 2009||Snecma||Rotary cutting tool comprising two cutting portions having opposed cutting directions|
|US7665935 *||Feb 23, 2010||Precorp, Inc.||Carbide drill bit for composite materials|
|US8562261 *||Mar 23, 2009||Oct 22, 2013||Sumitomo Electric Hardmetal Corp.||End mill|
|US9393629 *||Jun 13, 2011||Jul 19, 2016||Element Six Abrasives S.A.||Cutter elements, rotary machine tools comprising same and method for making same|
|US20030147711 *||Feb 7, 2002||Aug 7, 2003||Risen Carl W.||Bit for cutting drywall|
|US20050123363 *||Dec 9, 2003||Jun 9, 2005||The Boeing Company||Shaper router and method|
|US20050135887 *||Dec 17, 2003||Jun 23, 2005||Borschert Bernhard W.||Twist drill|
|US20060045637 *||Sep 1, 2004||Mar 2, 2006||Berkshire Precision Tool, Llc||Helical flute end mill with multi-section cutting edge|
|US20070280792 *||Jun 1, 2006||Dec 6, 2007||Onsrud Cutter Lp||Polycrystalline diamond tool for cutting|
|US20070286691 *||Jun 8, 2007||Dec 13, 2007||Franken Gmbh & Co. Kg Fabrik Fur Praezisionswerkzeuge||Cutting tool|
|US20080145158 *||Dec 13, 2006||Jun 19, 2008||Ching-Ching Chen||Milling Cutter|
|US20080152447 *||Mar 7, 2008||Jun 26, 2008||Snecma||Rotary cutting tool comprising two cutting portions having opposed cutting directions|
|US20090022561 *||Jul 18, 2007||Jan 22, 2009||Winebrenner John Richard||Rotary cutting tool|
|US20100196108 *||Mar 23, 2009||Aug 5, 2010||Sumitomo Electric Hardmetal Corp.||End mill|
|US20130209184 *||Jun 13, 2011||Aug 15, 2013||Element Six Limited||Cutter elements, rotary machine tools comprising same and method for making same|
|US20130294852 *||May 1, 2012||Nov 7, 2013||Seco Tools Ab||Compression cutting tool|
|CN104271295A *||Apr 30, 2013||Jan 7, 2015||山高刀具公司||压缩切削刀具|
|WO1994008745A1 *||Oct 13, 1993||Apr 28, 1994||Sandvik Ab||End mill tool with a compound material core and a hard material coating|
|WO2007142859A2 *||May 29, 2007||Dec 13, 2007||Onsrud Cutter||Polycrystalline diamond tool for cutting|
|WO2014007609A1 *||Jul 1, 2013||Jan 9, 2014||HOFMAN, Jan, Enno||Beveling / chamfering tool - router head for metal|
|U.S. Classification||408/230, 407/54, 407/53|
|International Classification||B23B51/08, B23B51/02|
|Cooperative Classification||B23C2210/0492, B23C5/10, B23C3/12, Y10T408/9097, Y10T407/1948, B23B51/02, B23B2251/043, Y10T407/1946, B23B51/08|
|European Classification||B23B51/02, B23B51/08|
|Mar 6, 1989||FPAY||Fee payment|
Year of fee payment: 4
|Aug 12, 1993||FPAY||Fee payment|
Year of fee payment: 8
|Aug 5, 1997||FPAY||Fee payment|
Year of fee payment: 12